Method for making a power connection

ABSTRACT

The invention provides systems and methods for power connection, which may be a sealed power connection. The sealed power connection may be used with an electric machine or any device that may require electrical and/or mechanical connection for power. The sealed power connection may provide an effective electrical connection while providing a robust mechanical connection. The electric machine or device may be fluid-sealed and/or fluid-cooled. The sealed power connection may provide for electrical insulation of the connection from the machine or device enclosure, and may also be sealed to provide for fluid sealing and/or internal fluid cooling of the electric machine or device, as well as fluid cooling of the connection.

CROSS-REFERENCE

This application is a divisional of U.S. Ser. No. 12/860,716, filed onAug. 20, 2010, which is a continuation-in-part application of U.S. Ser.No. 12/708,500, filed Feb. 18, 2010, to which application we claimpriority under 35 USC §120, and which claims the priority of U.S.Provisional Application Ser. No. 61/154,316, dated Feb. 20, 2009 whichare incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

High power electric machines and other high power electric devicesrequire robust power connections capable of reliably transferring highcurrents and insulating high voltages. In the case of fluid-sealedmachines or devices, the connection also requires sealing against themachine or device enclosure to prevent fluid from entering or exitingthe enclosure through any of the connection interfaces. In the case ofinternally fluid-cooled machines or devices, the connection requiressealing against the machine or device enclosure to prevent leakage ofcooling fluids.

One traditional method used for making power connections to electricmachines is to provide a threaded stud constructed of material withrelatively high electrical conductivity, such as copper or brass,connected to the internal wiring of the machine. With this method, asillustrated in FIG. 1, the threaded stud 10 is inserted through aninsulated block 11. The assembly is then inserted through the machinehousing wall 17 and captured with an insulated washer 12 and locking nut13. The power connection is completed by securing the power cable ringlug connector 14 with additional locking nuts 15, 16 which applypressure against the other locking nut 13.

One drawback for this stud connection design is that the threaded stud10 and locking nut 13 need to be constructed of material with relativelyhigh electrical conductivity, especially when used in high currentapplications. However, materials with high electrical conductivity tendto also have low mechanical yield strength properties, making them proneto failure when threaded hardware is used to secure the electricalconnection, and thus may not survive many assembly and disassemblycycles without damage.

Additionally, another drawback of a traditional stud connection designis that the electrical current must flow through the threads of thelocking nut 13 to the threads of the stud 10 to complete the electricalcircuit, providing only limited line contact and not much surface areacontact. This is especially troublesome in high current applications,where the limited electrical contact may result in additional resistivelosses that may lead to overheating of the connection.

Another traditional method for making power connections is the terminalconnection or “flying lead” method. This method, as shown in FIG. 2,involves terminating the internal wiring of an electric machine 17directly with a ring lug connector 18. The external power connectioncable for the machine is also terminated with a ring lug connector 19.These ring lug terminations 18, 19 are then connected together with athreaded fastener 20 and nut 21, or with a threaded fastener 20 to aterminal strip acting as the nut. The threaded fastener 20 and nut 21apply pressure between the contacting surfaces of the ring lugconnectors 18, 19 to complete the electrical path.

This method allows for an improved electrical connection over the studconnection design, because pressure is applied between the two largesurfaces of the ring lug connectors 18, 19. This produces an effectiveconnection with low resistance and high current capacity.

However, with the terminal connection method, because the two sets ofwires are directly connected external to the machine, a method is neededto seal the wires as they exit the machine through the machine housingor other enclosure wall in the case of a fluid-sealed machine. In thiscase, the entire connection may need to be accessible, yet may also needto be contained in some type of sealed enclosure, making this designapproach undesirable where a compact form factor is important.

Thus, a need exists for a method of high power connection that mayachieve a robust electrical and mechanical connection interface. Afurther need exists that may addresses the issue of sealing theconnection for fluid-sealed and/or internally fluid-cooled machines ordevices.

SUMMARY OF THE INVENTION

The invention provides systems and methods for power connection, such assealed power connection. Various aspects of the invention describedherein may be applied to any of the particular applications set forthbelow or for other types of power connections that may requireelectrical and/or mechanical connection. The invention may be applied asa standalone system or method, or as part of an application, such asproviding connections for high power electric machines, which may alsobe fluid-cooled machines. It shall be understood that different aspectsof the invention can be appreciated individually, collectively, or incombination with each other.

In accordance with one aspect of the invention, the power connection mayprovide an efficient electrical and robust mechanical connection. Thepower connection may include a power cable connector that may beconfigured to contact a power connection block. The power cableconnector and power connection block may be formed of electricallyconductive materials. The power cable connector and power connectionblock may contact one another over a relatively large surface area, andmay be electrically and mechanically connected. The power connection mayinclude a fastener assembly formed of a relatively high strengthmaterial. The fastener assembly may be mechanically connected to thepower connection block, and may be used to apply pressure to form theconnection between the power cable connector and power connection block.The fastener assembly may provide a robust mechanical connection, butneed not be part of the electrical connection formed by the power cableconnector and the power connection block.

In accordance with an aspect of the invention, a power connection may beprovided. The power connection may comprise a fastener assembly formedof a material with a first strength (S₁) and a power connection blockformed of a material with a second strength (S₂), wherein the fastenerassembly is mechanically connected to the power connection block, andwherein (S₁) is greater than or equal to (S₂). In some embodiments, thepower connection block may be formed of a material with a firstelectrical conductivity (EC₁) and the fastener assembly may be formed ofa material with a second electrical conductivity (EC₂), wherein (EC₁) isgreater than or equal to (EC2).

In accordance with another aspect of the invention, the power connectionblock may be fluid-cooled. For instance, the sealed power connection maybe used for an electric machine or device that may have internal fluidcooling. The cooling fluid may contact the power connection block.

The sealed power connection may also provide insulating and sealingconfigurations in accordance with another aspect of the invention. Aninsulator may electrically insulate the connection provided between thepower cable connector and the power connection block from the enclosureof an electric machine or device. The design may also provide a sealedconnection that may prevent cooling fluid used to cool the powerconnection block, or other fluids within the electric machine or device,from leaking out of the electric machine or device, or may prevent anyother fluids from entering or exiting the machine or device.

Another aspect of the invention may be directed to a method of makingpower connections to an electric machine. The method may includeproviding a power connection block in electrical communication with aninternal component of the electric machine; contacting a power cableconnector to the power connection block; and providing a fastenerassembly, wherein the faster assembly holds the power cable connectoragainst the power connection block, and wherein a greater amount ofelectric current flows through the power cable connector and the powerconnection block than through the fastener assembly. In someembodiments, the fastener assembly may comprise an insert, which may bepositioned within the power connection block, and a mechanical fastener,which may be a threaded fastener and which may be screwed in to theinsert.

Other goals and advantages of the invention will be further appreciatedand understood when considered in conjunction with the followingdescription and accompanying drawings. While the following descriptionmay contain specific details describing particular embodiments of theinvention, this should not be construed as limitations to the scope ofthe invention but rather as an exemplification of preferableembodiments. For each aspect of the invention, many variations arepossible as suggested herein that are known to those of ordinary skillin the art. A variety of changes and modifications can be made withinthe scope of the invention without departing from the spirit thereof.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 shows a traditional stud connection.

FIG. 2 shows a traditional terminal (“flying lead”) connection.

FIG. 3A shows an exploded view of a sealed power connection inaccordance with one embodiment of the invention.

FIG. 3B shows a cross-sectional view of a sealed power connection inaccordance with one embodiment of the invention.

FIG. 3C shows an exterior view of a sealed power connection inaccordance with one embodiment of the invention.

FIG. 3D shows a perspective view of a sealed power connection inaccordance with one embodiment of the invention.

FIG. 4 shows an example of applying a sealed power connection onto anelectric machine in accordance with one embodiment of the invention.

FIG. 5A shows current flow through a traditional stud connection method.

FIG. 5B shows current flow through a traditional terminal connection.

FIG. 5C shows an example of current flow through a sealed powerconnection in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

While preferable embodiments of the invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention.

The invention provides systems and methods for power connection (alsoreferred to herein as a sealed power connection, although someembodiments may not require the power connection be sealed). The powerconnection may be used in any application, including, but not limitedto, electric machines or devices that may require electrical and/ormechanical connection for power. For example, power may be provided by apower source, which may be external or internal to the electric machineor device, and may be transferred through the power connection to orfrom the internal wiring or components of the electric machine ordevice. Thus, power connections may be used in any type of electricmachine or electric/electronic device application.

FIG. 3A shows an exploded view of a sealed power connection inaccordance with one embodiment of the invention. For instance, athreaded fastener 6 may be tightened against a washer 8, which may comeinto contact with a power cable connector 7. The power cable connector 7may come into contact with a power connection block 4, which may beformed from material with high electrical conductivity. The powerconnection block 4 may include a high strength insert 5, which may beformed from a high yield strength material such as steel, that mayprovide mechanical support and/or connection for the threaded fastener6. Additionally, an insulator 1, which may be formed of a dielectricmaterial, as well as one or more seals 2, 3 may come into contact withthe power connection block 4 and/or insulator 1.

1. Electrical and Mechanical Connection

A sealed power connection assembly may include components that mayprimarily provide an electrical connection and components that mayprimarily provide a mechanical connection. For example, a sealed powerconnection assembly may include an electrical connection assembly thatmay include a power cable connector 7 and a power connection block 4, aswell as a mechanical connection assembly that may include an insert 5and a fastener 6. A sealed power connection may include both electricaland mechanical connection components, such that the power connection mayprovide an effective electrical connection as well as a robustmechanical connection.

The sealed power connection may provide an advantageous design for anelectrical connection in accordance with one aspect of the invention. Anelectrical connection may be accomplished by surface pressure contactbetween the power cable connector 7 and the power connection block 4.The power cable ring lug connector and/or power cable connector,referred to herein, may be any type of power connection component ormechanism known in the art that may contact the power connection blockfor the purpose of transferring electrical power to and/or from theconnection block. In some embodiments, the power connection component ormechanism may or may not be in electrical communication with a powercable, but may also be part of and/or transfer power from any type ofstructure or component known in the art that may be capable ofconducting and/or transferring power, such as bus bar.

The power connection block 4 may be constructed from material with highelectrical conductivity. For example, the power connection block may beformed of a material which may have an electrical conductivity of 10×10⁶S/m or greater, 30×10⁶ S/m or greater, or 50×10⁶ S/m or greater. In someinstances, the power connection block may be formed of copper, brass,silver, gold, aluminum, or any combinations or alloys thereof. The powerconnection block may be plated, clad, or include layers or components ofvarious materials, including elemental metals. The power connectionblock may be formed of, or may include, an elemental metal or any otherelectrically conductive material. The power connection block may beconnected to the internal wiring or components of an electric machine ordevice. The power connection block may be connected to the internalwiring or components by any type of electrical connection known in theart or later developed. For example, the power connection block may beconnected to the internal wiring or components by soldering, welding,brazing, swaging, adhesives, pressure connections, or any form ofmechanical connection, such as a threaded fastener, terminal strip, orany form of insert.

A mechanical fastener 6 may provide pressure between the powerconnection block 4 and the power cable connector 7. In some embodimentsof the invention, the pressure provided by the mechanical fastener maybe constant or substantially constant.

This sealed power connection may allow for a relatively large surfacecontact area for the connection interface in a compact space. Forinstance, the interface between the power cable connector 7 and thepower connection block 4 may be relatively large as compared to aninterface that may be provided by threads of a fastener. The sealedpower connection design may enable the contact area for the interfacebetween the power connection block and the power cable connector to beselected to support a desired amount of current flow. In some instances,a relatively large contact area may be selected to support a relativelyhigh current flow. In one example, the contact area between the powercable connector and the power connection block may be about 0.1 cm² orgreater, 0.5 cm² or greater, 1 cm² or greater, 2 cm² or greater, 3 cm²or greater, 4 cm² or greater, 5 cm² or greater, or 100 cm² or greater.In some other examples, the contact area may be greater than or equal toone tenth, one eighth, one quarter, one half, five eighths, threequarters, seven eighths, nine tenths, or may cover substantially all ofthe side of the power connection block that is in contact with the powercable connector.

For example, with this design, a connection using a 19 mm circular powercable ring lug connector 7 with a 10 mm threaded fastener 6 may becapable of transferring over 1600 A peak current in a three-phase ACinduction machine application, without exceeding generally acceptablethermal limitations of the connection. Additionally, the powerconnection block 4 may be cooled by fluid contacting the powerconnection block on the indicated area shown in FIG. 3B, which mayfurther increase the current transferring capability of the connection,to be discussed in greater detail below.

The sealed power connection may also provide an advantageous design fora robust mechanical connection in addition to the advantageous designfor the electrical connection. Generally, achieving optimal electricaland thermal performance for a high power connector requires the use ofmaterials which have high electrical conductivity. However, materialswith high electrical conductivity usually tend to also have lowmechanical yield strength properties, making them prone to failure whenthreaded hardware is used to secure the electrical connection. Thesealed power connection, in accordance with an embodiment of theinvention, may resolve this problem by the addition of a high yieldstrength material, which may not be part of the primary electricalcircuit.

The reliability of the clamping interface for the sealed powerconnection may be enhanced by the use of a high strength steel insert 5,or insert of other relatively high yield strength material, assembledinto the high electrical conductivity material which may compose thepower connection block 4. For instance, the insert may be formed ofplain high carbon steel AISI 1060 0.6% carbon, structural steal alloyASTM A36, high strength alloy ASTM A514, high tensile prestressingstrands, stainless steel AISI 304, or any other types of steel.Furthermore, in addition to steel, the high strength insert may beformed of any other material with the desired mechanical strengthproperties, including, but not limited to, titanium, bronze, aluminum,brass, tungsten, aramid (Kevlar or Twaron), nickel-chromium alloy(Inconel X750), or combinations or alloys thereof (e.g., titanium alloy(6% Al, 4% V), aluminum alloy 2014-T6). The insert 5 need not have highelectrical conductivity, and thus may be formed from any material withthe desired mechanical strength properties, which may be electricallyconductive or electrically non-conductive. In some embodiments, theinsert may have a yield strength of 100 MPa or greater, 300 MPa orgreater, 500 MPa or greater, 800 MPa or greater, or 1000 MPa or greater.

In a preferable embodiment of the invention, the insert may be threadedon the inside to allow the threaded fastener 6 to connect with theinternally threaded portion of the insert. Since the fastener 6 and/orthe insert 5 may be formed of a high strength material, this may enablea strong, robust mechanical connection. For instance, the use of highstrength materials may enable tightening of the threaded fastenerwithout damaging the threads of the fastener. This may enable theconnection to survive many assembly and disassembly cycles withrelatively little or no damage. In some embodiments, the fastener 6 maybe formed of the same material or a different material from the insert5. In some embodiments, the fastener may be formed of a high strengthmaterial, such as those described for the insert. The fastener 6 neednot have a high electrical conductivity, and thus may be formed from anymaterial with the desired mechanical strength properties, which may beelectrically conductive or electrically non-conductive. Any fastenerassembly may be provided. In some instances, the fastener assembly maycomprise an insert and/or a fastener.

In some embodiments, the power cable connector 7 and/or the powerconnection block 4 may be formed of material of a higher electricalconductivity than material used to form the fastener 6 and/or insert 5.For example, the power connection block may have an electricalconductivity (EC₁), which may be greater than the insert's electricalconductivity (EC₂) and greater than the fastener's electricalconductivity (EC₃). Furthermore, the electrical conductivity of thepower connection block may be greater than the electrical conductivityof any type of fastener assembly that may be used with the connection.

Also, in some embodiments, the fastener 6 and/or the insert 5 may beformed of material of higher strength than material used to form thepower cable connector 7 and/or the power connection block 4. In oneimplementation, a fastener assembly may be formed of one or morematerials of higher strength than the material used to form the powercable connector and/or power connection block. For example, a fastenerassembly may have a strength S₁ and the power connection block may havea strength S₂, and S₁ may be greater than or equal to S₂. Similarly, apower cable connector may be formed of a material of strength S₃, and S₁may be greater than S₃. The fastener assembly may include an insertformed of a material of strength S_(a), and a mechanical fastener may beformed of a material of strength S_(b), where at least one of S_(a) orS_(b) are greater than or equal to at least one of S₂ or S₃.

A threaded fastener 6 may be able to be repeatedly tightened against awasher 8 and power cable connector 7, without damaging the threads orcompromising the performance of the power connection block 4. In someinstances, a serrated Belleville washer may be used, which may functionas a locking mechanism for the fastener. The use of a serratedBelleville washer 8 with the connection may have several advantages,including: 1) it may provide a constant spring clamping force as thejoint may heat or cool and expand or contract during operation, and 2)the serrated Belleville washer may dig into the mating materials toresist rotation, and may thus prevent loosening of the connectioninterface due to vibration and other dynamic fatigue.

In some embodiments, other connection configurations may be used. Forexample, a fastener 6 may be tightened against the power cable connector7 without the use of a washer. For instance, the fastener 6 may directlycontact the power cable connector 7. Alternatively, other components maybe included in the place of, or in addition to, a washer. Any type offastener locking method or mechanism known in the art may be used withthe connection. For example, some form of spring structure, or elasticmaterial may provide a constant or substantially constant clampingforce. Any other components may be used that may assist with themechanical connection.

In an alternate embodiment of the invention, a fastener 6 may not needto be threaded, but may have another connection mechanism that mayenable it to connect to an insert 5. Any mechanical connectionconfiguration known in the art may be used. For example, the fastenerand insert may have some sort of lock and groove mechanism that mayprovide a robust mechanical connection. The fastener could also somehowsnap into the insert, or may have a toothed configuration, that mayenable the fastener to slide in and engage with the insert, but mayprevent it from disengaging. The fastener and the insert may have aconfiguration that may allow the mechanical assembly and disassemblybetween the fastener and the insert.

Preferably, an insert 5 may be affixed to the power connection block 4.The insert may be positioned within the power connection block. In oneembodiment, a threaded insert may be screwed into the power connectionblock. A connection block assembly may include components that mayprimarily involve an electrical connection, such as the power connectionblock 4 and components that may primarily involve a mechanicalconnection, such as the insert 5. The insert may be affixed to the blockby any of the mechanisms or methods known in the art or discussedrelating to fastening components. For example, the insert may haveexternal threads that may allow it to screw into or mate withcorresponding threads on the interior of the power connection block, orany other mechanical locking device may be used. The insert may be a keylocking insert (Keenserts) or a helical insert (Heli-Coil). In anotherexample, the insert may be a captive nut or mechanically fastened to thepower connection block based on the shape of the insert and/or powerconnection block. For example, the power connection block may have a lipor component that may prevent the insert from sliding out. The insertmay be self-tapping or pressed into the power connection block. In otherembodiments, the insert may be welded, brazed, or soldered into thepower connection block.

The insert 5 may be a tubular insert. For example, the insert may have asubstantially cylindrical exterior. The exterior of the insert may besmooth, threaded, ridged, or have any texture. The interior of a tubularinsert may have internal threads that may enable it to mechanicallyconnect to the fastener. The insert could also include any othermechanical locking device known in the art. The insert may be a screw orlocking fastener, which may or may not include threads. The insert mayalso have a shape, such as a square shape, or other geometric shape,protrusion or indentation, and the interior of the power connectionblock may have a corresponding shape that may prevent the insert fromrotating or otherwise moving within the power connection block. In someembodiments, the insert may be affixed to the power connection block byadditional mechanical components or devices that may secure the insertto the power connection block, or by adhesives, locking compounds ormaterials, or any other affixing means known in the art.

2. Fluid Cooling

Another aspect of the invention may also provide a sealed powerconnection that may advantageously allow for fluid cooling of theconnection. The use of fluid to cool the power connection block 4 mayprovide two distinct advantages over prior art designs:

1) The cooling fluid may remove heat from the power connection block 4,which may lower the operating temperature of the connection. This maynot only lower the average temperature of the power connection block 4,but may also lower the peak hot spot temperature. Thus, fluid cooling ofthe connection may provide for a higher peak current density rating forthe connection and may also improve the performance and reliability ofthe connection at any given continuous current density. The loweroperating temperature may also lower the electrical resistance of theconnection, which may provide for a more efficient power connection.

2) The active cooling may reduce temperature fluctuations and maymaintain a more constant operating temperature of the connection.Reducing temperature fluctuations may reduce the stress on themechanical joint (e.g., between the fastener 6 and the washer 8 or powercable connector 7) and may thus improve reliability of the connection,as thermal expansion and contraction of the connection materials may bereduced.

FIG. 3B shows a cross-sectional view of a sealed power connection inaccordance with one embodiment of the invention. As indicated, the powerconnection block 4 may be cooled by a fluid. The fluid may directlycontact the power connection block. Fluid may or may not be flowingwhere the fluid is contacting the power connection block. In someembodiments, the fluid may contact the surface of the power connectionblock opposite the threaded fastener. In some embodiments, the fluiddoes not contact the threaded fastener, insert, or any part of thefastener assembly. Alternatively, the fluid may contact one or morecomponents of the fastener assembly. The sealed power connection mayalso be designed such that fluid may also contact the power connectionblock on other portions of its surface, including external and/orinternal surfaces, which may include passages or cavities within theconnection block.

The fluid may be flowing against one or more surfaces that it contactsand/or the fluid may be substantially stationary in contact with one ormore surfaces. The fluid may flow perpendicular to or along any surfacethat it contacts. The fluid may flow at any angle to any surface that itcontacts. The rate of fluid flow may or may not be adjusted orcontrolled to provide a desired amount of cooling or temperaturecontrol. For example, a fluid flow rate may be increased to increase therate of cooling of the connection. In some instances, any surface areaof the power connection block that the fluid may contact may be designedto support a desired amount of heat transfer.

In some embodiments, the fluid may be contained within an enclosure ofan electric machine or device. In other embodiments, the fluid may ormay not be provided from a source external to the electric machine ordevice. In some embodiments, the fluid may be substantially stationarywithin the machine or device enclosure. Alternatively, it may move orcirculate within the machine or device, while contained within theenclosure, or may circulate external to the machine or device as well.

The cooling fluid may be any fluid known in the art. In someembodiments, the cooling fluid may be a gas, such as air; or a liquid,such as water, oil, or a liquid dielectric fluid; or a vapor or mist ofany such fluids; or any other fluid. For instance, a transmission fluid,such as automatic transmission fluid (ATF) may be used. A fluid may beselected according to desired thermal, electrical, chemical, or flowproperties.

In some embodiments, one or more surfaces of the power connection blockmay include one or more features that may aid in heat transfer, such asfins, grooves, channels, ridges, protrusions, bumps, indentations,patterns, textured surfaces, or any other surface feature. This mayincrease the exposed surface area of the connection block, which mayincrease the amount of surface area in contact with a fluid. This mayadvantageously provide for a greater degree of heat transfer between theconnection block and the fluid. In some instances, surface features mayassist with directing or channeling the fluid flow over and/or aroundvarious surfaces of the connection block. Alternatively, one or more ofthe connection block surfaces may be smooth or substantially smooth.

3. Insulating and Sealing Design

The sealed power connection may allow for a robust insulator and sealingdesign and method in accordance with another aspect of the invention.The power connection block 4 may be electrically insulated from amachine or device enclosure. For example, the sealed power connectionmay be used with an electric machine that may have a housing formed ofan electrically conductive material. Because electric machines mayoperate at voltages in excess of 400 V AC peak, an adequate insulationpath may be needed between the machine housing and the power connectionblock 4.

The insulator 1 may be formed of a dielectric material. In someembodiments, a fiberglass composite material may be used, such as FR-4glass reinforced epoxy or any other type of fiberglass reinforced epoxylaminate. Any other electrically insulating material may be used. Forexample, some preferable materials may include, but are not limited to,ceramic, glass, plastic, epoxy resin, synthetic resin bonded paper(SRBP, FR-1, and FR-2), epoxy-glass materials, or any combinationthereof. The insulator may be formed substantially of a dielectricmaterial or may include a dielectric coating or layer.

FIG. 3C shows an exterior view of a sealed power connector in accordancewith one embodiment of the invention. The term “exterior” may beprovided by way of reference only and shall not limit the placement ororientation of a sealed power connector. For instance, a sealed powerconnector may be fastened to an electric machine, and part of the sealedpower connection may be exposed to the exterior of the machine.Alternatively, the opposite side of the sealed power connection may beexposed to the exterior of the machine. In other embodiments, any sideor sides, or portion of any side or sides, of a sealed power connectionmay be within a machine, external to the machine, or exposed to theexterior of the machine.

The insulator may be fastened to a surface of an electric machine ordevice. For example, the sealed power connection design may providesecure clamping of the insulator 1 by multiple threaded fasteners 9 ontoa machine surface. Any number of threaded fasteners may be provided,such as four fasteners. In other implementations, the insulator may befastened to the machine surface by any other designs or methods known inthe art including, but not limited to, screwing it into the machinehousing, having some sort of mechanical connection such as a snappingconfiguration, having an interlocking configuration, using rivets, usingnuts, using some sort of clamp, using an adhesive or epoxy or any otherfastening mechanisms or methods known in the art. Any robust method ofattachment may be used to secure the insulator to any surface of amachine or device.

The sealed power connection may enable the connection to be fluid cooledwhile also providing a sealing design and method that may preventcooling fluid leakage, or may prevent any other fluid from entering orexiting through the connection interfaces. For example, one or moreseals 2, 3 may be provided. Any type of sealing mechanism orconfiguration known in the art may be used. For example, the seals maybe o-rings and may be placed as shown in FIG. 3B. Alternatively, theseals may be placed at any other location that may prevent fluidleakage. The seals may also be formed of other materials such as aputty, caulking, or filling materials.

The insulating and/or sealing of the sealed power connection may beenhanced by the shape of the insulator 1 and/or power connection block4. For example, the insulator 1 may have square features on its insidesurface, which may interface with squares features on the outside of thepower connection block 4, which may prevent rotation of the powerconnection block 4. For example, as shown in FIG. 3A, the powerconnection block 4 may include one or more square shaped features.Corresponding square shaped features on the interior of the insulator 1may match the square shaped features of the power connection block 4 toprovide a substantially snug connection that may not allow the two partsto rotate or otherwise move relative to one another. These features mayadvantageously prevent loosening or damage of the connection interfacesduring assembly of the mechanical connection and/or when the connectionmay be used in applications where the connection may be exposed tovibration or repetitive motion.

In some embodiments, the power connection block and/or insulator mayhave other shapes. For example, a power connection block may have ahexagonal shape or feature, and the insulator may have a correspondinghexagonal shape on its interior. In some instances the power connectionblock may have any concave or convex shape and a corresponding shape maybe provided by the insulator interior. In some implementations, thepower connection block may have a shape that may rotate but may have afeature that may prevent it from rotating; e.g., the power connectionblock may have a circular shape but may have a protrusion or indentationthat may correspond to the shape of the insulator interior that mayprevent it from rotating.

The relative shapes of the power connection block and the insulator maynot match up entirely in some embodiments of the invention. For example,the power connection block and insulator may have shapes that may matchup to some extent to prevent rotation, but may have additional featuresthat may provide gaps between the power connection block and insulatorinterface. For example, both a power connection block and insulator mayhave a square shape on its exterior and interior respectively, but thepower connection block may provide grooves or other features that mayenable fluid to flow between a portion of the power connection block andinsulator and thereby provide additional surface area to cool the powerconnection block. Grooves or gaps may also be provided between theinsulator and power connection block that may be used for otherpurposes, such as connection to internal wiring.

The insulator may also include a retaining feature that may locate thepower connection block 4 by means of a retaining ring, fastener, or anyother method know in the art, so as to capture the power connectionblock 4 into the insulator 1. Thus, the retaining feature may engage thepower connection block in position with regard to the insulator and mayprevent the power connection block from disengaging from the insulator.The insulator may also include locating features 10 on the insulator,which may insulate the passage of the connection through a machine ordevice enclosure wall, as well as locate the insulator and connectionassembly onto the machine or device enclosure surface.

FIG. 3D provides a perspective view of a sealed power connection as itmay appear when assembled in accordance with one embodiment of theinvention.

4. Electric Machine

The sealed power connection may be used to make power connections to anelectric machine. In some embodiments of the invention, the electricmachine may be a motor, such as a three-phase AC induction motor.Alternatively, the electric machine may be any sort of motor, generator,or any sort of machine that may require some form of electrical andmechanical power connection. In some embodiments, the connection mayprovide power from a source external to the machine to one or morecomponents inside machine, or the connection may provide power from asource within the machine to one or more devices outside the machine. Inother embodiments, the connection may provide electrical and mechanicalconnections between any two components which may both be external to themachine or within the machine.

The electric machine may also be any machine that may be fluid-sealed orfluid-cooled or that may have some sort of fluid in its interior. Insome embodiments, the machine may have fluid for cooling and/orlubrication. The fluid within the electric machine may be flowing or maybe substantially stationary. In some embodiments, the fluid within theelectric machine may circulate through the electric machine and may comefrom a source external to the electric machine. In other embodiments,the fluid may be contained within the electric machine and/or maycirculate within the electric machine.

The electric machine may utilize high power electrical connections.Reliable high power connections may require low-resistance electricalcontact with acceptable current density. Typical maximum currentdensities in copper DC power connections may be on the order of 2.2×10⁶A/m². This may typically limit the temperature rise of the connection tounder 30° C. in ambient temperatures over 40° C. See e.g., ANSIC37.20C-1974, IEEE standard 27-1974. In copper three-phase AC powerconnections, maximum peak current densities of 7×10⁶ A/m² havetraditionally been used in electric machines reliably. In someembodiments of the invention, fluid cooling may be introduced to one ormore connector surfaces, which may enhance the connection reliabilityand which may make it possible to exceed the 7×10⁶ A/m² value.

FIG. 4 shows an example of applying a sealed power connection onto anelectric machine (where some of the fastening hardware may have beenexcluded for clarity). For example, one or more power connection blocks4 may be connected to internal wiring of the electric machine. A housingof the electric machine may be provided. The housing may include any andall structures and/or components that may surround all or part of themachine and may perform the function of containment, support, and/orprotection, or any other similar functions, for the electric machine orany of the individual components of the electric machine. In someembodiments, all or part of the housing may be fluid-sealed. One or moreinsulators 1 may be connected to the housing of the electric machine andalso to one or more power connection blocks 4. An insulator 1 may beconnected to the housing by fasteners (e.g., such as the fasteners 9shown in FIG. 3C), and may be positioned between the housing and thepower connection block 4 to provide an electrically insulating barrier.Thus, the power connection block may be electrically isolated from theelectric machine housing. A power cable connector may be contacting thepower connection block or in electrical communication with the powerconnection block. In some embodiments, the power cable connector may belocated external to the machine housing.

For example, sealed power connections may be positioned at the end of anelectric machine. In some implementations, a plurality of sealed powerconnections may be arranged to form a roughly circular configuration.Sealed power connections may be placed at one or more sides or surfacesof a machine. In some embodiments, rather than being placed on anexternal housing of a machine, a sealed power connection may be usedwithin a machine. Any number of sealed power connections may be providedfor an electric machine, and may be positioned at any location on and/orwithin the electric machine.

5. Current Flow

The sealed power connection may provide an advantageous current flow andbeneficial design for electrical connection. The sealed power connectionmay be compared with the current flow of traditional connection methods.

For example, traditionally, many electric machines feature threaded studtype designs for electrical connections. Current flow through these studconnection designs may be illustrated by a schematic as shown in FIG.5A. For instance, current may flow into a ring lug connector 14, acrossan interface between the ring lug connector 14 and a locking nut 13, andthen through a threaded interface between the locking nut 13 and thethreaded stud 10.

As discussed previously, this current flow is undesirable because thecurrent must flow through the mechanical screw threads. The threadsprovide line contact with much lower surface area contact than largerflat surface interfaces, leading to higher resistance through theconnection. Additionally, because of the nature of the traditional studconnection assembly, the current must flow across two or moreinterfaces. These interfaces may include the interface between the ringlug connector 14 and the locking nut 13, and the interface between thelocking nut 13 and the threaded stud 10. Current flow across multipleinterfaces may be less desirable, as this method tends to have higherresistance than connection methods which only have a single interfacethrough which current may flow.

The nature of the current path through the threaded interface in a studconnection design may be driven by the need to electrically insulate theconnection assembly from the mounting surface of the enclosure wall 17.An insulated washer 12 and insulated block 11 are required to isolatethe electric current conducting components from the machine enclosurewall 17 in this stud connection method.

In another example, electrical connections in some electric machines mayalso be handled by another traditional design that involves directlyconnecting wire leads from the internal wiring of the machine to thepower connection cables. Current flow through this traditional terminalconnection or “flying lead” design may be illustrated by the schematicrepresented in FIG. 5B.

In the traditional terminal connection method, current 23 flows throughthe power connection cable 22 and into a ring lug connector 19. The wirelead from the internal wiring of the machine 17 is also terminated witha ring lug connector 18. The electrical connection is made by using athreaded fastener 20 and nut 21 to apply pressure between the two ringlug connectors 18 and 19. Current flows across the interface between thetwo ring lug connectors 18 and 19 and then through wire lead 17 to theinternal wiring of the machine.

Although the traditional terminal connection method can be designed tobe electrically and mechanically robust, it is difficult to seal andcool. Typically, the terminal connection is contained within a separatejunction box, or implemented using a terminal strip attached to theoutside of the machine, contained inside an additional accessibleenclosure. Difficulty with sealing the wires as they exit the machine orenclosure is a typical problem. The use of an additional enclosureattached to the outside of the machine also adds undesirable extra size,weight, and mechanical complexity to the machine.

This problem may be most significant with regard to power-densemachines. With power-dense machines, large conductors are required tohandle the high electrical current, yet the overall size of the machineis much smaller than conventional machines of comparable power.Therefore, a large junction box or connection enclosure cansignificantly increase the size and weight of the power-dense machine,where compact form factor and low weight are important design criteria.Thus, a traditional terminal connection method may be undesirable inparticular circumstances.

FIG. 5C shows an example of current flow through a sealed powerconnection in accordance with an embodiment of the invention. The sealedpower connection may provide electrical connectivity between a powersource and the internal wiring or components of an electric machine ordevice. The current 24 may flow from an input power cable, or any otherpower source, into a ring lug connector 7 and across an interfacebetween the ring lug connector 7 and a power connection block 4. Athreaded fastener 6 may provide pressure between the ring lug connector7 and the power connection block 4, which may create a low resistanceconnection with a relatively high surface area contact. Current may flowacross the interface of the ring lug connector 7 and the powerconnection block 4 to the internal wiring 25 or components of theelectric machine or device to apply power to the machine or device.

The sealed power connection design may advantageously include a largesurface area contact between the power cable connector 7 and the powerconnection block 4 which may provide for: 1) high current capacity ofthe connection interface, 2) a relatively large thermal mass of thepower connection block 4 that may absorb and conduct heat away from theconnection, and 3) compactness and simplicity of the overall connectionassembly.

Also, as discussed previously, the threaded fastener 6 may beconstructed of a high yield strength material with low electricalconductivity, because the fastener need not be included in the primarypath of the current flow. Additionally, a threaded insert constructed ofhigh yield strength material may also be introduced into the matingthreads of the power connection block 4, and may also be separate fromthe primary current flow path, achieving a highly robust mechanicalconnection in addition to the excellent electrical connection.

Thus, FIG. 5C may illustrate a method of sealed power connection whichmay provide electrical connection. The method of sealed power connectionmay include receiving a current 24 at a connector 7, allowing currentflow between the connector and a power connection block 4, and conveyingcurrent from the power connection block to internal wiring 25. Themethod of sealed power connection may also provide mechanicalconnection. The method of sealed power connection may thus also includeproviding a fastener 6 that may mechanically connect to an insert 5 thatmay be mechanically connected to the power connection block 4. Themethod of mechanical connection may assist with the electricalconnection.

The sealed power connection method illustrated in FIG. 5C mayadvantageously have compact features, and effective electrical contactand current flow. A superior mechanical connection may also be achieved,along with the ability to robustly secure and seal the connectionassembly to a machine or device enclosure, as well as provide cooling tothe connection when integrated with an internally fluid cooled machineor device.

It should be understood from the foregoing that, while particularimplementations have been illustrated and described, variousmodifications can be made thereto and are contemplated herein. It isalso not intended that the invention be limited by the specific examplesprovided within the specification. While the invention has beendescribed with reference to the aforementioned specification, thedescriptions and illustrations of the preferable embodiments herein arenot meant to be construed in a limiting sense. Furthermore, it shall beunderstood that all aspects of the invention are not limited to thespecific depictions, configurations or relative proportions set forthherein which depend upon a variety of conditions and variables. Variousmodifications in form and detail of the embodiments of the inventionwill be apparent to a person skilled in the art. It is thereforecontemplated that the invention shall also cover any such modifications,variations and equivalents.

What is claimed is:
 1. A method of making power connections to anelectric machine comprising: providing a power connection block inelectrical communication with an internal component of the electricmachine; contacting a power cable connector to the power connectionblock; and providing a fastener assembly, wherein the faster assemblyholds the power cable connector against the power connection block,wherein a greater amount of electric current flows through the powercable connector and the power connection block than through the fastenerassembly.
 2. The method of claim 1, wherein the fastener assemblycomprises an insert and a mechanical fastener.
 3. The method of claim 2,wherein the insert is retained within the power connection block.
 4. Themethod of claim 3, wherein the mechanical fastener is a threadedfastener, which is screwed into the insert.
 5. The method of claim 1,wherein at least one of the power connection block or the power cableconnector is formed of a material with greater or equal electricalconductivity than the material used to form at least one of thecomponents of the fastener assembly.
 6. The method of claim 1, whereinat least one of the components of the fastener assembly is formed of amaterial with greater or equal strength than the material used to format least one of the power connection block or the power cable connector.7. The method of claim 1, wherein the power connection block is incontact with a cooling fluid.
 8. The method of claim 7, wherein all orpart of the electric machine is contained within a machine housing. 9.The method of claim 8, wherein the cooling fluid is within the machinehousing.
 10. The method of claim 1 further comprising: providing aninsulator in contact with the power connection block, wherein all orpart of the electric machine is contained within a machine housing, andwherein the insulator is capable of electrically insulating the powerconnection block from the machine housing for the power connection. 11.The method of claim 10, wherein the power cable connector is locatedexterior to the machine housing.
 12. The method of claim 10, wherein theinsulator and power connection block are sealed, such that fluid isprevented from leaking through the interface between the powerconnection block and the insulator and through the interface between thepower connection and the machine housing.